Purpose::
It has been shown that matrix metalloproteinase-9 (MMP-9) isinvolved in loss of ganglion cells, while knockout of MMP-9protects against these changes. This led to our interest indetermining whether the Morrison model could be adapted to investigatethe possible neuroprotective effects of MMP-9 knockout in mice.

Methods::
30 MMP-9 KO mice and 30 matched controls were obtained fromJackson Labs and elevated intraocular pressure was induced throughinjection of hypertonic saline into the episcleral vessels usingthe Morrison model. We injected the right eye only and usedthe left eye as a control in each animal. IOP was measured weeklyin conscious mice using a TonoLab rebound tonometer. When thegroup average change of IOP was greater than 600 mmdays, wecollected control and treated eyes under sedation. Optic nervecross sections were stained with toluidine blue. Axon countswere obtained in a masked fashion for both control and treatedeyes using the Zeiss KS400 Image Analysis system and % axonsurvival was calculated and tested for significance with theStudent’s t-test.

Conclusions::
As previously shown by others, KO of MMP-9 shows some neuroprotectiveeffect in the setting of elevated IOP. We have shown that theMorrison model can be successfully adapted to use in mice inour hands and will be a useful tool for further investigatingthe pathophysiology of MMP-9 involvement in axon loss in glaucoma.